1. Field of the Invention
The present invention relates to an antiskid control apparatus for controlling the brake force of a vehicle, based on wheel speeds of the respective wheels.
2. Related Background Art
There are a variety of suggestions about vehicle control apparatus for controlling the vehicle, based on rotational speed signals of the wheels outputted from speed sensors set at the respective wheels, and there exists the antiskid control apparatus as a typical example. Electromagnetic induction type speed sensors are used commonly for detecting the rotational speeds of the wheels in this antiskid control apparatus. The electromagnetic induction type speed sensors are sensors making use of the phenomenon in which rotation of a gearlike sensor rotor causes magnetic flux passing in a coil provided in the sensor to vary with time and generate ac voltage of a frequency proportional to the rotational speed of the sensor rotor.
Incidentally, in cold districts road heaters for snow melting are buried in road surfaces of hills or the like in order to prevent a skid of wheels. Specifically, as illustrated in FIG. 4, road heaters 64 for snow melting are buried under the surface of uphill road 60 and under the surface of downhill road 62, for the purpose of melting snow on the road surfaces and preventing freezing of the road surfaces by heat from the road heaters 64, thereby preventing a skid of wheels.